The industrial chemistry of fats & oils is a mature technology, with decades of experience and continuous improvements over current practices. Natural fats & oils consist mainly of triglycerides and to some extent of free fatty acids (FFA). Many different types of triglycerides are produced in nature, either from vegetable as from animal origin. Fatty acids in fats & oils are found esterified to glycerol (triacylglycerol). The acyl-group is a long-chain (C12-C22) hydrocarbon with a carboxyl-group at the end that is generally esterified with glycerol. Fats & oils are characterized by the chemical composition and structure of its fatty acid moiety. The fatty acid moiety can be saturated or contain one or more double bonds. Bulk properties of fats & oils are often specified as “saponification number”, “Iodine Value”, “unsaponification number”. The “saponification number”, which is expressed as grams of fat saponified by one mole of potassium hydroxide, is an indication of the average molecular weight and hence chain length. The “Iodine value”, which is expressed as the weight percent of iodine consumed by the fat in a reaction with iodine monochloride, is an index of unsaturation.
Some typical sources of fats & oils and respective composition in fatty acids are given by way of example in Table 1.
TABLE 1SymbolCotton-CoconutCornPalmPeanutPalmLinseedRiceRape-OliveSaturatedCaproic 6:00.40.2Caprylic 8:07.33.3Capric10:06.63.5Lauric12:047.847.80.2Myristic14:00.918.116.30.11.10.40.02Palmitic16:024.78.910.98.511.644.16.019.83.910.5Margaric17:00.05Stearic18:02.32.71.82.43.14.42.51.91.92.6Arachidic20:00.10.11.50.20.50.90.60.4Behenic22:03.00.30.20.2Lignoceric24:01.00.20.1TOTAL28.091.922.782.020.3509.023.36.813.87UnsaturatedMyristoleic14:1 w-5Palmitoleic16:1 w-70.70.50.10.20.6Heptadecenoic17:1 w-150.09Oleic18:1 w-917.66.424.215.438.037.519.042.364.176.9Linoleic18:2 w-653.31.658.02.441.01024.131.918.77.5Linolenic18:3 w-30.30.747.41.29.20.6Gadolenic20:1 w-91.00.50.51.00.3TOTAL72.08.177.318.079.7509176.793.286.13PolyunsaturatedRicinoleic18Rosin acids—% FFA0.5-0.61.0-3.51.70.10.82-1425-150.5-3.80.5-3.3Soy-Sun-LinolaLardButterfatTallowTallCastorJatrophaSaturatedCaproic2Caprylic2Capric3Lauric0.50.53.5Myristic0.10.21.5113Palmitic11.06.85.626262621.014.6Margaric0.50.5Stearic4.04.74.013.51122.511.07.4Arachidic0.30.420.5Behenic0.1LignocericTOTAL15.512.69.642.060.552.03.52.022.0UnsaturatedMyristoleic0.5Palmitoleic0.10.1422.50.8Heptadecenoic0.530.5Oleic23.418.615.9432643163.047.5Linoleic53.268.271.892.51.5204.228.7Linolenic7.80.52.00.540.31.0Gadolenic10.5TOTAL84.587.490.458.037.548.054.57.578.0Polyunsaturated24Ricinoleic89.5Rosin acids40% FFA0.3-1.60.1-1.50.30.55-20
There are other potential feedstock available at this time, namely trap and sewage grease and other very high free fatty acid greases who's FFA can exceed 50%.
The main sources of fats & oils are palm and palm kernels, soybeans, rapeseed, sunflower, coconut, corn, animal fats, milk fats.
Potentially new sources of triglycerides will become available in the near future, namely those extracted from Jatropha and those produced by microalgues. These microalgues can accumulate more then 30 wt % of lipids on dry basis and they can either be cultivated in open basin, using atmospheric CO2 or in closed photobioreactors. In the latter case, the required CO2 can originate from the use of fossil hydrocarbons that are captured and injected into the photobioreactor. Main sources of fossil CO2 are power stations, boilers used in refineries and steamcrackers furnaces used to bring hydrocarbon streams at high temperature or to supply heat of reactions in hydrocarbon transformations in refineries and steamcrackers. In particular steamcracking furnaces produce a lot of CO2. In order to enhance the CO2 concentration in flue gases of these furnaces, techniques like oxycombustion, chemical looping or absorption of CO2 can be employed. In oxycombustion, oxygen is extracted from air and this pure oxygen is used to burn hydrocarbon fuels as to obtain a stream only containing water and CO2, allowing concentrating easily the CO2 for storage or re-utilisation. In chemical looping, a solid material acts as oxygen-transfer agent from a re-oxidation zone where the reduced solid is re-oxidised with air into oxidised solid to a combustion zone, where the hydrocarbon fuel is burned with the oxidised solid and hence the effluent resulting from the combustion zone only contains water and CO2. Absorption of CO2 can be done with the help of a lean solvent that has a high preferential to absorb CO2 under pressure and typically at low temperature and will release the CO2 when depressurized and/or heated. Rectisol® and Selexol® are commercial available technologies to remove and concentrate CO2. Other sources of CO2 are the byproduct from carbohydrates fermentation into ethanol or other alcohols and the removal of excess CO2 from synthesis gas made from biomass or coal gasification.
US 2007/0175795 reports the contacting of a hydrocarbon and a triglyceride to form a mixture and contacting the mixture with a hydrotreating catalyst in a fixed bed reactor under conditions sufficient to produce a reaction product containing diesel boiling range hydrocarbons. The example demonstrates that the hydrotreatment of such mixture increases the cloud point and pour point of the resulting hydrocarbon mixture.
US 2004/0230085 reports a process for producing a hydrocarbon component of biological origin, characterized in that the process comprises at least two steps, the first one of which is a hydrodeoxygenation step and the second one is an isomerisation step. The resulting products have low solidification points and high cetane number and can be used as diesel or as solvent.
US 2007/0135669 reports the manufacture of branched saturated hydrocarbons, characterized in that a feedstock comprising unsaturated fatty acids or fatty acids esters with C1-C5 alcohols, or mixture thereof, is subjected to a skeletal isomerisation step followed by a deoxygenation step. The results demonstrate that very good cloud points can be obtained.
US 2007/0039240 reports on a process for cracking tallow into diesel fuel comprising: thermally cracking the tallow in a cracking vessel at a temperature of 260-371° C., at ambient pressure and in the absence of a catalyst to yield in part cracked hydrocarbons.
U.S. Pat. No. 4,554,397 reports on a process for manufacturing olefins, comprising contacting a carboxylic acid or a carboxylic ester with a catalyst at a temperature of 200-400° C., wherein the catalyst simultaneously contains nickel and at least one metal from the group consisting of tin, germanium and lead.
It has been discovered a process to make bio-naphtha in an integrated biorefinery from all kinds of natural triglycerides or fatty acids. In said process crude fats & oils are refined, either physically or chemically, to remove substantially all non-triglyceride components and non-free fatty acids.
The use of a biofeed is a possible solution in the search of alternative raw material for the naphthacracker. Nevertheless, using this type of feed can lead to corrosion problems and excessive fouling because of oxygenates forming from the oxygen atoms in the biofeed. Also existing steamcrackers are not designed to remove high amounts of carbonoxides that would result from the steamcracking of these biofeedstock. According to the present invention, such a problem can be solved by hydrodeoxygenating/decarboxylating (or decarbonylating) this biofeed before its injection into the steam cracker. Thanks to this hydrodeoxygenation/decarboxylation (or decarbonylation), the negative effect due to the production of CO and CO2 and traces of low molecular weight oxygenates (aldehydes and acids) in the steam cracker is reduced.
Another advantage is of course the production of bio-monomers in the steam cracker.